1. Field of the Invention
This invention relates to a remote supervision and control system.
2. Description of the Prior Art
Conventional systems for supervising and controlling from a remote place between, for example, a central supervision unit and a plurality of console units can be largely classified into the following systems: (1) a polarized signal system wherein one connecting line is alloted to each object to be supervised and controlled in addition to two common lines and the kind of signal is discriminated by the polarity of the voltage impressed on the connecting line, (2) a synchronous selection system wherein an orderly sequence is provided for objects to be controlled and the objects to be controlled are synchronously switched in turn by pulses sent through a common connecting line to control and supervise the objective units, (3) a pulse code system wherein pulses are sent out through a common connecting line and the kind of signal is judged by the number of the pulses, different pulses combined in them or stop of the pulses to control or supervise the units, (4) a frequency system wherein signals of different frequencies are oscillated, sent out through a common connecting line and judged by using a frequency filter to control and supervise the units, and so on. However, each system has its own merits and demerits.